In a manufacturing process of a semiconductor device, film formation is often carried out on a semiconductor wafer (hereinafter, referred to as a “wafer”) as a substrate by atomic layer deposition (ALD). A film forming apparatus that performs the ALD, may be configured such that a wafer is loaded on a rotary table installed in a vacuum container, and the wafer that rotates by rotation of the rotary table repeatedly passes through an atmosphere where a raw material gas is supplied and an atmosphere where a reaction gas that reacts with the raw material gas is supplied, thereby performing film formation.
In the film forming apparatus, for example, a shower head is installed to face the rotary table, and the raw material gas is discharged from a discharge port of the shower head to form the atmosphere of the raw material gas. In order to separate the atmosphere of the raw material gas from the atmosphere of the reaction gas, for example, in the shower head described above, an exhaust port and a discharge port of a purge gas are installed so as to surround the discharge port of the raw material gas such that the exhaust and the discharge of the purge gas are performed. The film forming apparatus having such a shower head is known in the art.
When a film is formed using the film forming apparatus having the shower head, a film thickness of an end portion on the central side of the rotary table and a film thickness of an end portion on the circumferential end side of the rotary table may become smaller than a film thickness of other portions, with respect to a film thickness in the plane of the wafer when the rotary table is viewed in a radial direction. It is considered that this is based on the fact that a relatively large amount of the raw material gas supplied to each of these end portions is exhausted without being adsorbed to the wafer because the exhaust from the exhaust port is performed near the end portion on the central side and the end portion on the peripheral edge side of the rotary table in the plane of the wafer, when the wafer is moved to a position facing the shower head by rotation of the rotary table.